Process of and apparatus for washing coal and other minerals



A. FRANCE 1,758,035

PROCES OF AND APPARATUS FOR WASHING COAL AND OTHER MINERALS May 13,.1930.

Filed Nov. 3, 1925 Patented May 13, 1930 PATENT OFFICE ANTOINE FRANCE, OF LIEGE, BELGIUM PROCESS OF AND APPARATUS FOR WASHING GOAL AND OTHER MINERALS Application filed November 3, 1925, Serial No. 86,596; and in Belgium April 23, 1925.

The present invention relates to an im provement in processes of washing coal and other minerals, of the kind wherein the material to be treated, is subjected to the action of a so-called liquid conveying stream in one or several launders along which are arranged a plurality of upward stream sorting apparatus or separators, and the invention more particularly relates to an improved process for the treatment of coal and other minerals wherein the constituents of .the highest specific gravity only form a relatively small proportion of the raw material to be treated.

In the processes of the kind just referred to the material, under the influence of the conveying stream, becomes classified in several layers of particles of varying specific gravities, the layer formed by the, particles of the highest specific gravity being on the bottom of the launder and the Various other layers of particles of gradually lower specificgravity being superposed one above the other, the layer of particles of the lowest specific gravity being uppermost.

In practice, only three main layers are taken into consideration, i. e. that of the concentrates, that of the mixed product, and that of the waste when the raw material consists of ores, or that of the slaty material, that of the intermediate products, and that of the clean coal when the material to be treated consists of coal. For greater facility, the terms slaty material, intermediate products and clean coal will, in a purely conventional sense, he used in the following description to designate the aforesaid three main layers, it being expressly understood that the invention is not limite to the washing of coal only, but also applies to the preparation of ores and other similar materials.

The material stratified as explained above is conveyed along by the liquid stream in the launder, and at intervals the. bottom oi the latter is interrupted by slots extending across the whole width of the said launder and un-' der which are disposed the upward stream sorting apparatus or separators. By means of the separators are successively Withdrawn the products settling on the bottom of the launder, and it is usual to provide a first series of separators for withdrawing the slaty material, and a second series situated downstream in relation to the first for withdrawing the intermediate products, while the clean coal is discharged at the lower end of the launder, which has a slight downward slope 'in the direction of the conveying stream.

From the above explanations, it will be readily understood that the washing will be so much more eflicient that the material brought above the various separators will be freer from particles belonging to another category of material, that is to say for instance that the slaty material to be withdrawn'by means of the separators provided for the withdrawal of such material will reach the latter in auniform and homogeneous condition, without containing any particles of the intermediate category.

In practice, it is generally possible to attain this result by a suitable adjustment or arrangement of the usual known plant to which reference is .made above, but, however, When the products to be treated are of such a nature that the quantity of constituents of high specific gravity is rather. small, it becomes impossible even by reducing the number of the separators intended for the withdrawal of the slaty material,-to with- 30 draw by means of such separators products of high specific gravity which are ideally concentrated, or in other words to avoid the discharge by the said separators together with the constituents of high specific of a certain quantity of constituents of another category.

The present invention mainly resides in the intentional addition to the raw material to be treated of an auxiliary material of high specific gravity of suitable size and nature, in order that the thickness of the layer constituted by the constituents of high specific gravity together with the said auxiliary material, over the slots of the separators, may be sufficient to provide that the separators for the withdrawal of the slaty material will only discharge an ideally concentrated material. The auxiliary material of high specific gravity mixed with the discharged material of high specific gravit contained in the raw material is subsequent y recovered if required by any convenient method (for instance by means of an electro-magnet, or by screening) and re laced'at the top of the launder in order to be again added to the raw product to be treated.

In order that the invention may be more readily understood, some instances of application of the said invention will now be described with reference to the accompanying drawings, but it is to be observed that the invention is not restricted to the materials mentioned or to the construction of plant illustrated and that any suitable material or any suitable plant may be adopted according to the needs of the various individual cases of application of the invention.

In the drawings, Fig. 1 illustrates in a purely diagrammatic manner an embodiment of plant for carrying out the process according to the invention, while Fig. 2 shows in a purely diagrammatic manner a modified embodiment of plant for carrying out the said process, both plants being more particularly intended for washing coal.

Referring first to Fig. 1, a represents the lowest launder of a plant for washing fine coal (for instance from 0 to inches), consisting of a plurality of superposed launders with separators discharging into the launder immediately underneath that from which they depend.

It will be assumed here for illustrative purposes that the auxiliary material of high specific gravity adopted is for instance quartz or feldspar, well screened in grains of half an inch.

The quartz or feldspar is fed at b and immediately settles on the bottom of the laun-' der.

Along the latter is arranged a first series of upward stream separators 0 serving to withdraw clean constituents of high specific gravity, and then a second series of similar separators 01 serving to withdraw intermediate products which, together with the last constituents of intermediate specific gravity discharged by way of a slot 6, are directed into a cistern f, whence they are, for the purpose of re-washing according to a known process, brought back by means of an elevator 9 into the launder a at a point situated immediately downstream in relation to the point of feeding of the raw material to be treated, which is contained in a supply hopper it. On the raw material being fed to the launder the slaty constituents from 0 to inches concentrate in the interstices between the grains of quartz or feldspar and form with the latter a layer of material of high specific gravity which arrives in a perfectly homogeneous condition over the separators c by which the said material of high specific gravity is discharged onto a stationary inclinedscreen i with square mesh of inches, on which the fine slaty constituents are separated from the quartz or feldspar by means of water sprays k, the slaty constituents passing through the screen i and dropping into a cistern m whence it is removed by known means, while the quartz or feldspar drops from the screen i into another cistern n where it is taken up by a bucket elevator p and returned by the latter at b in the launder a.

It is to be observed that the quantity of quartz or feldspar to be employed is small because the bed of concentrates of high specific gravity only moves very slowly along the launder a. By the described means it becomes possible considerably to increase the thickness of the said bed and thus to reduce the importance of the upward streams in the separators, as the product which reaches the slots over the latter is particularly well concentrated and the separation of the flat particles of high specific gravity is thereby facilitated.

In a plant for washing large coal, for instance coal over inches, there may be em ployed as intentionally added material of high specific gravity rather fine quartz or feldspar (for instances 1 3' inches) or even sand, and this offers the appreciable advantage of filling well the interstices between the large particles of high specific gravity and thereby preventing the fine clean coal which, owing to ineflicient screening, might be contained in the raw coal to be treated, from intermingling with the large particles of high specific gravity.

Fig. 2 illustrates a plant, with so-called wet sorting apparatus or separators, more particularly intended for washing coal from inches to 4 inches, but the auxiliary material of high specific gravity employed here to carry out the process according to the invention is nothing else than a determined proportion of constituents of high specific gravity which are withdrawn by means of the first separator c of the launder a and which, instead of being entirely discharged to waste by the elevator p, are in part discharged at the point I; of the launder a by way of the discharge chute 1'. In order to be able to regulate the proportion of constituents of high specific gravity thus used again as auxiliary material of high specific gravity, the size of the inlet of the chute '1' may be altered by means of a slidable baffle s movable by means of a screw to connected to the said baflie and operated by means of a hand wheel t.

If desired, the inlet of the chute r may be provided with a screen in order to redirect into the launder a only large-sized or smallsized constituents of high specific gravity, according to needs.

The constituents .of high specific gravity reintroduced at Z) into the launder a serve to increase the proportion of constituents of high specific gravity and by thus thickening the layer of such constituents on the bottom of the launder to obtain a more pronounced concentration of the material of high specific gravity, which ensures a cleaner separation of such material.

It should be expressly understood that the invention is not restricted to the instances just described and applies quite as well to the washing of ores. Its adaptability depends from the possibility of an auxiliary material of high specific gravity being available of which the price, the size, the nature and the specific gravity are such that they will permit of the said material being added to the constituents ofhigh specific gravity of the mate ,of underf the said cast iron granules being recovered by means of a screen with a mesh, or iron granules might be employed to form and thicken the layer of high specific gravity in the launder of a plant for concentrating zinc ore, the last-named granules being recovered by means of an electromagnetic device.

I claim:

1. The process of separating minerals having constituents of different specific gravities, consisting in forming a flowing stream of water and mineral of the kind specified havinginsuflicient of the constituent of high, est specificgravity to form a definite stratum, adding to said flowing stream material having a specific gravity adapting it to form a stratum including the highest specific gravity constituent, and in quantity suflicient to form therewith a definite stratum, permitting the mixture to stratify and then separating the lowest stratum.

2. The process of separating minerals having constituents of different specific gravities, consisting in forming a flowing stream of water and mineral of the kind specified having insuflicient of the constituent of highest specific gravity to form a definite stratum,

adding to said flowi'ng stream material having a specific gravity adapting it to form a stratum including the highest specific gravity constituent, and in quantity suflicient to form therewith a definite stratum, permitting the mixture tostratify and thenseparating the lowest stratum by gravity, at given moments of the process through discharge devices provided with ascending streams.

.3. The process of separating minerals having constituents of difierent specific gravities, consist-ing in forming a flowing stream of water and mineral of the kind specified having insuflicient of the constituent of highest specific gravity to form a definite stratum, separating the lowest stratum formed in the flowing stream, forming a second flowing stream with water and the thus separated lowest stratum, repeating these steps a number of times, adding to said flowing stream, at at least one moment of the process, material having a specific gravity adapting it to form a stratum including the highest specific gravity constituent, and in quantity sufficient to form therewith a definite stratum, permitting the mixture to stratify.

4. The process of separating minerals having constituents of different specific gravities, consisting in forming a flowing stream of water and mineral. of the kind specified having insufiicient of the constituent of highest specific gravity to form a definite stratum, adding to said flowing stream material having a specific gravity adapting it to form a stratum including the highest specific gravity constituent, and in quantity sufficient to form therewith a definite stratum, permitting the mixture to stratify, then separating the lowest stratum, separating therefrom the added material and re-adding same to the flowing stream. I

5. The process of separating minerals having constituents of different specific gravities, consisting in forming a flowing stream of water and mineral of the kind specified having insufiicient of the constituent of highest specific gravity to form a definite stratum, adding to said flowing stream material having aspecific gravity adapting it to form a stratum including the highest specific gravity constituent, and in quantity sufficient to form therewith a definite stratum, permitting the mixture to stratify, separating the lowest stratum formed in the first portion of the flowing stream, separating therefrom the added material, re-addingsame in the flowing stream, separating the lowest stratum formed in the subsequent ortion of the flowing stream and re-intro ucin'g same in the flowing stream.

6. The process of se arating minerals having constituents of di erent specific gravities, consistin in forming a flowing stream of water and mineralof the kind specified having insufficient of the constituent of highest specific gravity to form a definitestratum, separating the lowest stratum formed in the first portion of the flowing stream, adding same to the flowing stream in sufiicient and adjustable quantity to form therewith a definite stratum, permitting the mixture to stratify and separating the lowest stratum formed in the remaining portion of the flowing stream.

7. Plant for separating minerals having constituents of difierent specific gravities, comprising at least one suitably inclined launder, in which flows a stream of water and mineral of the kind specified having insufficient of the constituent of highest specific gravity to form a definite stratum, transverse slots in the bottom of said launder for separating the lowest stratum formed therein, a conduit collecting the products separated by the first slots, a second conduit branched on the first, and adjustable means in said second conduit to direct part of said separated products to waste and part into the launder without any further classification thereof Ether than that which took place in the laun- 8. Plant for separating minerals having constituents of different specific gravities, comprising at least one suitably inclined launder, in which flows astream of water and mineral of the kind specified, having insuificient of the constituent of highest specific gravity to form a definite stratum, transverse slotsin the bottom of said launder for separating the lowest stratum formed therein, a conduit collecting the products separated by the first slots, a second conduit branched on the first, adjustable means in said second conduit to direct part of said separated products to waste and part into the launder Without any further classification thereof other than that which took place in the launder, and means to return the lowest stratum separated by the subsequent slots, into the launder.

In testimony whereof I signed hereunto my name.

ANTOINE FRANCE. 

